Radio apparatus



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RADIO APPARATUS 16 Sheets-Sheet 15 Original Filed Dec Sept. 10, 1946. 5, Y. WHITE RADIO APPARATUS l6 Sheets-Sheet l5 Original Filed Dec. 8, 1942 IOOJ Sept. 10, 1946. 5. Y. WHITE RADIO APPARATUS Original Filed bec. 8, 1942 16 Sheets-Sheet 16 l I l I l I I I I I I I I H5 20 01a/ fal/braf/ons U 2 g MUQmBW I l I l I I I l I I25 30 Patented Sept. 10, 1946 RADIO APPARATUS Sidney Y. White, Wilmette, 111., assignor to Victor S. Johnson, Chicago, 111.; Alex Thomson, administrator of said Johnson, deceased Original application December 8, 1942, Serial No. 468,195.. Divided and this application October 15, 1943, Serial No. 506,372

20 Claims. I

This invention relates to radio apparatus, and is particularly, although not exclusively, concerned with mobile radio apparatus suitable for meeting the exacting requirements of military service on land, at sea, and in the air- Such apparatus may be carried on a wide variety of vehicles such, for example, as a truck, a tank, o a naval airplane catapulted from a cruiser. It may be subjected, therefore, to violent shock and to extreme and protracted vibration. Again it may be carried on the back of a soldier.

Such apparatus may be used in every condition of climate and weather to be found on the face of the earth, and in every season. It may be exposed to dust, mist, rain, sleet and snow from the air, and to mud and oil spray thrown up from roadways. It may be exposed to radical and abrupt changes of temperature, humidity and air pressure by being carried in the space of only a few minutes from a tropical desert into the substratosph'ere, or vice versa.

It is often desirable that many communication channels be made available, and that the distance at which a transmitter may be received shall be limited, in order that the same communication channels may be used in different .regions without the possibility of mutual interference, and also as a safeguard against listening in by the enemy. For these reasons, among others, it is often desirable that apparatus for military use be designed to operate in the ultrahigh frequency range. The ultra-high frequency range has important uses for non-military as well as military purposes, but its use imposes severe requirements.

The nature of these requirements may be well appreciated if the conditions met when tuning in a broadcast station on a home radio receiver are contrasted briefly with the conditions met in effecting communication between mobile units operating in the ultra-high frequency range.

The broadcast station is an elaborate and expensive, stationary installation, and is under the supervision of a staff of highly trained radio engineers. No pains or expense is spared to assure that the station is maintained precisely on the assigned frequency. The station is constantly on the air. The home set user can search for the station signal and can adjust the tuning to the signal when he finds it. The broadcast station, moreover, is allotted a kc. channel .which represents nearly one per cent of the entire standard broadcast band and approximately two-thirds per cent of the highest frequency at cent can be depended upon to bring in the desired station. For such simple and coarse operation, the dial is a mere convenience; it is by no stretch of the imagination a precision instrumentality relied upon to show the exact frequency for which the home receiver is set.

In the ultra-high frequency military field conditions are entirely diiferent, the requirements being incomparably more evere. The transmitter is not constantly in operation, so that there is no signal to search for. Contact must be established through pre-setting the transmitter and the receiver to the precise frequency assigned. There can be no twiddling of dial at the receiver. Where accuracy of tuning within one per cent would sufice to bring in the standard broadcast station, a one per cent error of tuning in the range of 150 me. would constitute an error of 1500 kc.; i. e., an error in excess of the entire standard broadcast frequency range, or enough to miss one hundred channels as there made available and fifty more besides. The same degree of inaccuracy that is permissible in tuning a home set to bring in a broadcast station would miss a range wider than the entire standard broadcast band. The further point should not be overlooked that the transmitter in accordance with the present invention, as well as the receiver, is generally a light, mobile unit, and is subject to the same limitations as the receiver. Since errors of the transmitter and the receiver may be equal and cumulative, the receive can not be allotted a tolerance representing more than one-half of the permissible lack of correspondence of transmitter and receiver frequency, because a like tolerance must be accorded to the transmitter.

In addition to the foregoing, these mobile transmitters and receivers are required to operate under varying conditions of power supply. The source of voltage may be a storage battery varying between 20 and volts; and the line voltage for operating A. C. transmitters and receivers may vary between and volts.

The crucial elements afiecting the precision and the permanence of precision of receiver tuning and of transmitter tuning are found in, or in close association with, the ultra-high frequency circuits. In accordance with the present invention these elements are chosen of such materials, are constructed in such forms, and are associated and combined with one another into a head unit in such manner that the influence of Q temperature changes upon frequency is drastically and definitely limited, and that such slight changes of frequency with temperature as do occur are unalterable, so that the initial limitation will be dependably maintained.

It is a salient feature of the present invention that the electrical elements of the head unit are mounted in an airtight housing in which they are rendered immune to dust, dirt and weather, and substantially free from changes of humidity and air pressure, the entire head structure being shock-insulated.

The head should desirably be capable of performing certainly and dependably without overhauling or readjustment for .a period {equal at least to the lives of the-tubes; namely, 500 hours of actual service, or one year of service in elapsed time.

It is the primary object of the present invention to provide universal head units for incorporation in radio receivers and transmitters, capable of pre-set dial tuning with the precision required to establish communication in the ultra-high frequency range, and capable of withstanding without detriment or permanent change, and even without temporary incapacity, the most severe conditions of every type of service, yet sufiiciently light and compact to admit of incorporation in transmitters and receivers intended to be used in aircraft or to be carried into action on the backs of soldiers.

It is a further important object of the invention to provide head units of the kind referred to which can be produced in quantity with liberal and comfortable manufacturing tolerances for most of the parts, in some instances tolerances of as much .as two per cent.

It is a still further important object of the invention to provide a head unit adaptable for operation in .any selected range from three to 600 megacycles, through the mere selection and insertion of a small unitary readily replaceable tuned circuit assembly and the selection and incorporation of a dial mechanism which is calibrated to cover the desired range.

Quantitatively, the more important requirement to be met in service are roughly (1) that the head shall be capable of pre-set tuning with an accuracy within one .10 kc, channel at 150,000

kc.; (2) that it shall suffer no detriment from ;;L

shocks of 8 Gs, such as will be encountered in a tank or when an airplane carrying the unit is catapulted from a cruiser; (3.) that it shall not be rendered inoperativenor temporaril incapacitated by vibration; (4.) that it shall not be temtion of two or more of the conditions referred to under (2) to (6.), inclusive.

Other objects and advantages will hereinafter appe r.

This application is a division of my pending pplication, Serial No. 468,195 filed December 8, 1.9512, for Precision radio app e p esent application is directed primarily to the features of rendering the apparatus immune to humidity changes and adaptable for operation in any one of a large number of frequency ranges. Features of the invention not claimed herein are disclosed and claimed in my parent application, Serial No. 468,195 and in other divisional applications thereof, to wit, Serial No. 506,373, filed October 15, 1943 for Radio apparatus, Serial No. 506,374, filed October 15., 1943, for Electrical condenser, Serial No. 506,375, filed October 15, 1943, for Method of lining up unicontrolled tuned radio apparatus, Serial No. 506,376, filed October 15, 1943, for Method of making inductance coils, Serial No. 506,377, filed October 15, 1943 for Method of limiting changes of frequency of tuned circuits in response to temperature changes and Serial No. 555,805, filed August 30, 1944, for Electrical condensers.

In the drawings forming part of this specification .Fig. Us a diagrammatic view illustrating principally circuits employed in a receiver which embodies features of the invention;

Fig. '2 is a view similar to Fig, 1 illustrating principally circuits employed in a transmitter which embodies features of the invention Fig. 3 is a horizontal sectional view illustrating important parts of the receiver unit;

4 is a fragmentary sectional view taken upon the line 4-4 of Fig. 3 looking in the direction of the arrows;

Fig. 5 is a view in side elevation, partly broken away, of the structure illustrated in Fig. 3;

Fig. 5a is a fragmentary View showing the thrust rod and tuning core assembly;

Fig. 6 is a transverse vertical sectional view taken upon the line li -6 of Fig. '51ooking in the direction of the arrows, the view beingon a larger scale than Fig. 5;

Fig. 7 is a fragmentary detail view of the structure'illustrated in Figs. 5 and '6;

Fig. 8 is a sectional view similar to Fig. 6 but taken on the line 8-8 of Fig 5 looking in the direction of the arrows;

Fig. 9 is a fragmentary detail sectional view taken upon the line 9-9 of Fig. 5 lookingin the direction of "the arrows;

Fig. 10 is atop plan view of a coil and condenser supporting plate employed in the transmitter and in the receiver;

Fig. 11 is a sectional View of the supporting block shown in 'Fig. 10, taken on the line lll| of Fig. 10 looking in the direction of the arrows;

Fig. 12 is .a sectional View of the block shown in Figs. 10 and 11 taken upon the line l'2l"2 of Fig. 11, looking in the direction of the arrows;

Fig. 13 is an end view of a coil form employed in both the transmitter and the receiver;

Fig. 14 is a plan view of the coil "form shown in Fig. 13;

Fig. 35 is a longitudinal sectional View showing the plate of Figs. 10 to 1'2 and the coil form of Figs. 13 and '14 in assembled relation and with a coil wound on the latter, the section beingtaken on the line |5l'5 of Fig. 17 looking in the direction of the arrows;

Fig. 16 is a plan view .of the coil assembly of Fig. 15;

Fig. 1'7 is a rear end view showing the: coil assembly of Figs. 15 and 16 'together'with an assoc iated tank condenser;

Fig. 18 is a view in side elevation of the coil and condenser assembly of Fig. 17;;

Fig. .19 is a bottom view of the coil and condenser assembly shown in Fig. 17;

Fig. .20 is a longitudinal sectional view showing details of the condenser of Figs. 17 to 19, inclusive;

Fig. 21 is a rear end view of a modified form of coil and condenser assembly;

Fig. 22 is a view in side elevation of the assembly of Fig. 21;

Fig. 23 is a sectional view taken upon the line 23-23 of Fig. 21 looking in the direction of the arrows;

Fig. 24 is a. rear end view of a further modified form of coil and condenser assembly;

Fig. 25 is a view in side elevation of the assembly of Fig. 24;

Fig. 26 is a sectional view taken upon the line 2626 of Fig. 24;

Fig. 27 is a sectional view taken upon the line 21-21 of Fig. 26 looking in the direction of the arrows;

Fig. 28 is a sectional view similar to Fig. 26 showing a further modified form of coil;

Fig. 29 is a rear end view of a modified form of coil and condenser assembly;

Fig. 30 is a View in side elevation of the assembly of Fig. 29; I

Fi 31 is a view in side elevation of a further modified form of coil and condenser assembly;

Fig. 32 is a sectional view, partly broken away intermediate its ends, of a condenser which may be advantageously employed in the transmitter and in the receiver;

Fig. 33 is a sectional view taken upon the line 33-33 of Fig. 32 looking in the direction of the arrows;

Fig. 34 is a graph illustrating the various relationship of tuning core movement in mils to the frequency in megacycles of circuits tuned and controlled by various diameter cores;

Fig. 35 is a graph showing mils of core movement required to change the frequency one megacycle in the range of 100 to 140 megacycles, for various coil and core combinations;

Fig. 36 is a fragmentary bottom plan view illustrating a coil assembly which includes a modified mounting of an adjustable permeable element that forms a part of the assembly;

Fig. 37 is a fragmentary view showing a composite core, as for instance iron and copper;

Fig. '38 is a view in sectional elevation of an unproved condenser which may be reduced in capacity to predetermined accuracy by grinding, and which may then be employed to advantage in the transmitter and in the receiver;

Fig. 39 is a plan view of the body of the condenser of Fig. 38;

Fig. 40 is a fragmentary view illustrative of a difficulty which the condenser of Figs. 38 and 39 is designed to overcome;

Fig. 41 is a fragmentary view in sectional elevation further illustrating the difficulty which the condenser of Figs. 38 and 39 is designed to overcome;

Fig. 42 is a fragmentary view in sectional elevation showing the grinding away of surplus capacity units of the condenser of Fig 38 to produce a condenser of the desired fixed capacity;

Fig. 43 is a fragmentary plan view illustrating the effect of the grinding of Fig. 42;

Fig. 44 is an end view of the oscillator assembly cooperating with any one of tuned circuit assemblies of Figs. 16 to 19, 21 to 28, and 29 to 31;

Fig. 45 is a view in elevation of the structure shown in Fig. 44 as seen from the left of Fig. 44;

Fig. 46 is a fragmentary view looking down on the structure of Figs. 44 and 45;

Fig. 47 is a sectional View taken on the line 41-41 of Fig. 44, looking in the direction of the arrows, and with the tube of Fig. 44 removed;

Fig. 48 is a graph provided for use in explaining the alignment of the receiver and/ or transmitter with the precalibrated dial;

Fig. 49 is a fragmentary detail View of mechanism employed in the train between the dial knobs and the tuning cores used after preliminary adjustments for securing and fixing the precise correspondence desired between the dial calibrations and the carrier frequency in megacycles at a multiplicity of predetermined points, as, for instance, every megacycle; and

Fig. 50 is a fragmentary sectional view taken upon the line 50-50 of Fig. 49 looking in the direction of the arrows.

An illustrative embodiment of the invention is shown in connection with a superheterodyne radio receiver for receiving radio waves of ultrahigh frequency. In Fig. 1 reference numeral I designates the antenna, 2 designates a 36 ohm coaxial transmission line. the outer conductor of which is grounded and is connected to a switch contact 3, while the inner conductor of the line is connected to a switch contact 4. A third switch contact 5 is provided, the aforesaid switch contacts cooperating with switch contacts 6, 1

. and 8 of a tuned circuit assembly 9. The assembly 9 comprises an inductance coil I 0, whose ends are connected to switch contacts 6 and 8 and a fixed condenser II, the tuning of the circuit to different carrier frequencies being effected by means of a movable core 12 which may be of the powdered iron type. An intermediate tap i3 on coil I3 is connected to switch contact I to provide a 35 ohm coupling point for the transmission line, the connection to switch contact 1 being designated by reference numeral M. The slope of the tuning curve of circuit 9 is adjusted to a desired value by means of a movable slug [5 positioned alongside the coil NJ, whose effect on the tuning of the circuit will be hereinafter described. The core I2 is adjusted by the operator to tune in the desired station by means of a unicontrol knob i3 associated With a precalibrated dial l7. In order that the resonant frequency of circuit 9 may be made to agree with the calibrations of dial i'i', adjustable means as indicated by the arrow i3 is provided whereby the relative position of the coil H and core I2 may be adjusted through a slight range independently of the dial setting. A full discussion of the manner of effecting the adjustments of elements I5 and I8 will be hereinafter described.

The voltage developed in circuit 9 is supplied to the control grid IQ of radio frequency amplifier tube VTI through the condenser 20. Grid 19 is connected through the circuit shown, including resistors El and 22 and filter capacitor 23 to a source of AVG voltage or source of bias potential such as the voltage source indicated at point A.

Capacitor 23 is of a type of construction. found highly advantageous and desirable, and universally employed by me in the ultra-high frequency range, and consists of a sheet of metal separated from the body of the set by a sheet of mica, forming a non-inductive bypass to ground. This form of construction insures freedom from unwanted resonant circuit combinations formed the wiring of the set and wherever a bypass condenser to ground is indicated in the drawings it is of this type. All leads have resistances in them, also to prevent formation of resonant loops. Resistance 22 is of the wire wound type being em bedded in a grounded metallic block 22a. (see Fig. 3) and acts as a radio frequency choke to prevent 7 all radio frequency voltage from entering the supply leads.

The tube VT! is supplied with the usual voltages for its electrodes andsuitably bypassed. The

plate of VTI is connected to a resonant mixer circuit :24 through a pair of switch contacts E i-26.

This circuit differs from circuit '9 mainly in the position of the tap 2'! on the coil '23 of the circuit, this tap being connected to switch contact 29, which engages a switch contact 3!! by means in dicated by reference numeral 3!,the construction of which will be hereinafter described in detail. The other connections of circuit 24 are similar to those of circuit 9 and are indicated by the same reference numerals. minimize grid circuit leading. Switch contact .5 is connected to a suitable source of B voltage through a resistor 32, and is also bypassed to ground as shown. The input and output circuits of VT! are electrically shielded from each other by a grounded shield as diagrammatically indicated at 33 in Fig. 1, and physically illustrated as frame member 95 in Fig. 3.

Mixer circuit 24 is tuned to the signal frequency by means of a second core l2 and the adjusting means 18 and for thi circuit are similar to those described in connection with circuit 9. Voltage is injected into the resonant mixer circuit 24 from a resonant oscillator circuit 34 whose coil 35 is mounted coaxially with the coil 28, and at a critical distance therefrom. Voltage is supplied to the signal grid 35 of mixer tube VT2 through the circuit shown including a condenser 31, and bias is supplied thereto through the circuit shown including resistors 383 the latter resistor being connected to bias point A. Suitable voltages are supplied to the other elements of tube VT2 through the circuits shown, and the output of the tube is connected to a resonant circuit 40, which in the illustrated embodiment of the invention is tuned to a frequency of 5.2 megacycles. Resonant circuit 40 i coupled to a transmission line 4| through a transformer 42 or other suitable coupling means, as it has been found desirable in some cases to allow for a considerable physical separation of the whole tun-- ing unit from its intermediate frequency ampliher and power supply, and also from its antenna.

The oscillator circuit shown is of the ultra-- audition type, which combines the advantages of requiring no feedback winding, as well as allowing grounding the heater and cathode. The fact that tuned circuit 34 is at high potential to ground is of little interest in core tuning, and grounding the cathode is of great practical advantage, as it has been found that the capacity from heater to cathode is effective in introducing circuit noises, which show up as frequency fluctuations in the oscillator if it is attempted to run the cathode at some potential higher than ground. The plate of tube VT3 is connected to one end of coil 35 through a pair of switch contacts 43-44, and the other end thereof is connected to the grid of the tube through the switch contacts 45-456 and capacitor 47. The oscillator grid 43 has a divided grid leak consisting of resistor 49, choke and resistor 5| to ground, and an isolation condenser 52. By suitable proportioning of resistor 49 and resistor 51 a negative voltage is built up at A suitable for supplying bias to the control grids of mixer tubes VTZ and/or vacuum tube V'I'l Tap 53 is brought out through switch contacts 55 and 56 by connector 54 and is energized through resistor 51 and choke 58 by a suitable The tap 2.1 is provided to source of .B voltage. Isolation is effected by condenser 59 in the usual manner. Capacitor .60 performs the same function as H in tuned circuits 9 and 24, but it has been found desirable to also employ .a condenser 61 for more complete thermal stability of the oscillator. The action of condenser 6| will be more fully discussed later herein.

The oscillator circuit 34 is tuned by means of a movable core l2a which is in turn operated through the adjustable connection l8 and control knob l6, thereby providing unicontrol tuning of the resonant circuit 9, mixer circuit '24 and oscillator circuit 34.

Th oscillator 62 of Fig. '2 shows the same general structure used as a transmitter instead of a receiver. The entire oscillator assembly 62 is identical in :every way with the oscillator assembly shown in .Eig. 1. It is possible at times that this oscillator will be fed with somewhat higher plate voltage. Its components and performance will be otherwise identical. The RF amplifier shown in Fig. 1 is physically reversed so that its input and output circuits are interchanged, forming the buffer tube 63. Its input circuit may well be untuned and a coil 28 used to pick up some energy from the oscillator for exciting the grid through the condenser 31, its grid leak being 38 as shown. The tube is energized in the usual way and its output goes to tuned circuit assembly 9 through the contacts 5 and 8. Tuning condenser H resonates this combination whose frequency is controleld also by the core l2 physically connected to the dial through the adjustable means 18. The output transmission line is connected .to the tuned circuit 9 through contacts 4 and '1, and plate voltage is applied to contacts 3 and B filtered by the condenser 23 and a resistor 22. Contact 3, being at ground potential to radio frequency by virtue of condenser v23, is connected to an output'transmission line shown through condenser 64 and contact 4, likewise connected to the line by condenser 65, the purpose of condensers 64 and 65 being to remove D. C. potential from the line.

This assembly, therefore, forms a very low power continuous wave transmitter, but its main use is to energize either a final stage or a buffer meeting a final stage to provide reasonable power outputs.

As has already been indicated, the crucial and significant parts of the transmitter and of the receiver from "the standpoint of this invention are those parts which control the frequency characteristics of the ultra-high frequency circuits of the structure, and those parts included in or closely associated with such circuits, which bear upon the precision of such control.

Important and significant elements, combinations and sub-combinations will be described and explained fully hereinafter. It is the present purpose to outline in a brief and general way the association with one another of the principal elements and assemblies and to describe the means for supporting and housing those elements in order that the place in the general scheme of the elements and combinations hereinafter described will be evident as the description proceeds.

The showing of Figs. 3 to 9, inclusive, is specifically of what may be termed the receiver head, but it is to be understood that the transmitter includes a similar .head, differing from the receiver head only in such minor details as will 

